Carriers of Rare Earth Elements in Pacific Deep‐Sea Sediments

Abstract

To determine carriers affecting the rare earth element (REE) composition of pelagic sediment, Pacific sediments were analyzed for major elements and REEs. The P and Ca concentrations correlate positively, and the Ca/P ratio is consistent with that of carbonate fluorapatite (CFA). In addition, P concentration correlates strongly with REE concentration, except for Ce, suggesting the significant influence of CFA on the bulk REE abundance of sediments. Many researchers have reported the important contribution of Asian source eolian dust (ASED) to Pacific sediments. On the basis of REE compositions of CFA and ASED, another carrier—“factor 3”—that controls the REE composition of sediments was estimated by the factor analysis. The North American Shale Composite–normalized REE pattern of the calculated additional carrier exhibits a convex shape with a peak around the middle REE. The REE composition of the additional carrier is similar to the composition of leachates from sediments by reductant and the composition of diagenetic Mn nodule, suggesting that the additional carrier is Mn oxide deposited during diagenesis. The contributions of ASED, CFA, and diagenetic Mn oxide to the REE compositions of sediments were estimated by multiple regression analysis. The ASED and CFA contribute mainly to sediments in the Pacific area north of 20°N and the equatorial Pacific region, respectively. The contribution of factor 3 is slightly high in the northern Pacific region, the vicinity of the Hawaiian Islands, and the equatorial Pacific region.